Currently, action mechanisms of the same style are mounted in keyboard musical instruments for performing a hammer action, such as a piano, although the action mechanisms are somewhat different from one keyboard musical instrument to another concerning a standard. That is, an English style action mechanism called the pushing-up style is employed in a modern piano.
However, in the nineteenth century, an action mechanism of the German style or the Viennese style called the jumping-up style was widely known as other mechanisms aside from this pushing-up style. Such a mechanism in the past, the historical transition of the jumping-up style to be described later, and the like are discussed in a book entitled "Vom Hammer" written by Walter Pfeiffer and published in 1979 (third edition). Further, the inventor of the present invention was interested in a keyboard musical instrument of this style and was inspired to start the manufacture of such a keyboard musical instrument by seeing photographs of a musical instrument Orphica, before confirming the contents of this book (approximately fifteen years ago).
Basic characteristics of this jumping-up style is that a rotational central axis of a hammer is attached to a key. The most important progress in an action mechanism of this jumping-up style was made in the eighteenth century. That is, Johann Andoreas Stein (1728 to 1792) devised excellent touch of playing by mounting tongue-like components independent for each key instead of parts to which beak-like protrusions of hammers existing in the rearward of keys that were arranged in a fixed rail shape hook on. This was the most important advance of the jumping-up style action mechanism, and determined the jumping-up style action mechanism.
The Stein's action mechanism did not have a back-check (an object serving to stop the motion of a hammer that strikes a string and jumps back after striking the string). However, it may be considered that it was Stein's achievement to have created the basic form of the German style action mechanism and have determined a final form of an action mechanism that is hard to jump.
The world famous Viennese style action mechanism was taken over by Nanette who was Stein's daughter, and by her husband Johann Andoreas Streicher who was a manufacturer of keyboard musical instruments, and its originality was further developed. Therefore, the action mechanism was called the Viennese style instead of the German style when Stein's daughter Nanette got married to the Viennese man, and the action mechanism is often written as "the German Viennese style action mechanism" because both the German and Viennese styles have the same roots.
The improvement of Stein's style having the tongue-like components independent for each key (see, for example, FIG. 31) has very light touch (feeling of play), does not cause any sense of increased pressure by let-off (motion or function for separating the motion of a key and the motion of a hammer before the hammer and a string collide with each other) to a player, and is easy to repeat striking keys. A key has the depth of approximately 6 millimeters and the heaviness (a value in grams at which a key is depressed) of 30 grams in bass range and 20 grams in treble range.
On the other hand, when a key is depressed, a current piano experiences increase of relatively large resistance, i.e., force of a key to push back at the time of let-off. The depth of a key is 9.5 to 10 millimeters. A grand piano of Steinway is a typical one of the few pianos whose heaviness of a key is low at approximately 47 grams in average.
Although such an improvement was added to the jumping-up style action mechanism, the trend of the world was in favor of the pushing-up style. This is because a decisive improvement, which is now practical, was added to the English style action mechanism which is a pushing-up style. That is the repetition action mechanism, which was invented in 1821 and then was evolved into the current grand piano action mechanism by further improvement in 1840.
A piano action cannot be prepared for the next string striking unless a key rises to "a certain height" by a performer lifting a finger after the key is depressed to generate sound (a string is struck) once. The repetition action mechanism is a mechanism that is devised such that "a certain height" required for preparation of string striking is as low as possible. With this mechanism, the function of repeated striking (to make repeated striking easy) can be improved.
As far as the inventor of the present invention knows, upright pianos except limited models of two manufacturing companies in the world do not have this function. Therefore, this function is a point for comparing performability of an upright piano and a grand piano. This is called "Kurzhubwerk" in German, which means "the lifting height lowering function".
Moreover, the jumping-up style (the Vienna style) action mechanism had a critical structural problem. The inventor of the present invention also noticed the problem when the inventor tried to manufacture a keyboard musical instrument once approximately fifteen years ago, but did not notice that this problem is discussed in the literature "Vom Hammer" until recently. The structural problem that the Vienna style action mechanism has is namely that the rotational central axis of a hammer portion shifts in accordance with the movement of a key. This causes inconveniences described below.
Usually, it is common to assume the state in which a key is depressed to the lowest point when a string is struck, but a different state may be assumed, for example, a state in which a string is struck by instantly hitting a key with strong force. In other words, this state corresponds to staccato of forte.
In this case, although a hammer jumps up by the reaction of instant hit of a key with strong force to strike a string, the key is not in a state that it is fully depressed to the lowest point, but is somewhere on its way to the lowest point. In the Vienna style action mechanism, since the rotational central axis of the hammer is attached to the key, the position of the rotational central axis of the hammer at that time is in the position lower than the state where the key depressed is to the lowest point. As a result, since the positions of the rotational central axis of the hammer are different respectively in each of the above-mentioned two states, the hammer reaches the string forming different tracks in each state, and parts of the hammer head contacting the string are also different respectively.
Since a dislocation of the string striking point (the point where the hammer head contacts the string) arises in the longitudinal direction viewed from a performer, if strings are stretched in rows to cross the direction to which keys extend, the hammer not only does not strike an aimed string but may strike another string or a plurality of unnecessary strings of different sounds simultaneously. In addition, in the hammer side, since the large area of the hammer head contacts the strings at unspecified points, tones also become unstable and sound quality cannot be adjusted.
A Vienna style action mechanism 373 that adopts the above-mentioned jumping-up style is illustrated in FIGS. 31 through 34. As shown in FIG. 31, a keyboard body 305 having a keyboard portion (not shown) in the right side (in the figure) is swingably held by a pin 313 and a pedestal 315. A supporting pole 375 is provided at the other end portion of the keyboard body 305, and a base portion of a hammer body 377 is pivotally supported by a rotational central axis 378 at the top end of the supporting pole 375 to strike a string 307.
A beak-like projecting piece 379 is mounted on the base end portion of the hammer body 377. An engaging stepped portion 383 is formed in an escapement member 381 that is always biased toward this beak-like projecting piece 379 of the hammer body 377 by a spring bar 380. On the other hand, a back-check 389 is mounted on a frame 385 along the rotational track of the hammer portion 387 of the hammer body 377, and a sliding member such as leather is stuck on the surface of the back-check 389.
In a performance, as shown in FIGS. 32 and 33, the supporting pole 375 in the other end of the keyboard body 305 rises toward the string 307, and at the same time, the beak-like projecting piece 379 of the hammer body 377 and the engaging stepped portion 383 of the escapement member 381 are engaged, in accordance with the key striking operation of the keyboard portion. In this way, the hammer body 377 performs a striking pivotal operation against the string 307.
The engagement of the beak-line projecting piece 379 of the hammer body 377 and the engaging stepped portion 383 of the escapement member 381 is designed to be let off as shown in FIG. 33 immediately before the striking operation of the hammer body 377. The timing of this let-off can be adjusted exactly by an adjustment screw 391. When the performer sets the keyboard portion free, the let off beak-like projecting piece 379 descends while sliding against a return sliding surface 393 of the escapement member 381 as shown in FIG. 34, and returns to the state shown in FIG. 31. In addition, a hammer body 377, after striking the string 307, is caused to return in the direction of its original position by strong repulsion of the string 307, but the force of the movement is reduced by sliding friction between the hammer portion 387 of the hammer body 377 and the back-check 389, and the hammer body 377 stops. Therefore, the hammer body 377 does not rebound to strike the string 307 again.
The let-off of the Viennese style action mechanism 371 utilizes the shift of the rotational central axis 378 of the hammer body 377 in the longitudinal direction viewed from the performer by swinging movement of the keyboard body 305. That is, let-off is effected when the top end of the beak-like projecting piece 379 in the opposite side of the hammer portion 387 moves as if it is pulled out from the escapement member 381, by depressing the keyboard portion.
Therefore, the more a reliable movement of let-off is desired, the longer the shifting distance of the rotational central axis 378 must be made by separating the rotational central axis 378 from the keyboard body 305 and placing it in a higher position. In addition, since the back-check 389 is required to be placed correspondingly in a higher position as well, it is hard to design the action mechanism 373 to be low in height. Further, since it is necessary to provide the back-check 389 and to adjust its condition of striking, there is also a problem that the number of components and the number of assembly steps are many.
Moreover, in the conventional Vienna style action mechanism 373, since the entire action mechanism 373 protrudes to the other side of the keyboard portion by the length L (see FIG. 31) that includes the part from the striking point of the hammer portion 387 of the hammer body 377 to the mounting positions of the hammer body 377 and the escapement member 381, it is hard to design the entire keyboard musical instrument to be shallow in depth. In addition, when the hammer body 377 is larger, the rotational central axis 378 of the hammer body 377 must be placed in a higher position, which, on the other hand, results in larger dislocation of a string striking point on the hammer portion 387.